Better health based routing for transient reads

Right now replica selection for reads with transient replication is purely health based, but it is health based in the sense that it health information is shared across both transient and full ranges. This means you can't use the health information to tell if an endpoint will be faster for a specific query.

As a heuristic a transient replica will be a little faster for a read compared to a full replica given two endpoints with similar scores so maybe we don't need additional health information.